Electromagnetic motor



July 25, 1944. 'l J. A. 'rAYLoRErAL 2,354,483

' ELECTROMAGNETIC MOTOR Original Filed Aug. 6, 1941 5716. Z. JZZ'G. 5.ATTQRA Y.

Patented July 25, 1944 UNITED STATES PATENT OFFICE ELECTROMAGNETIC MOTOROriginal application August 6, 1941, Serial No. 405,724. Divided andthis application February 1, 1943, Serial No. 474,412

Claims.

Our invention relates to an electromagnetic motor and has particularreference to a long stroke electromagnetic reciprocating tool ndingparticular utility when employed as a soil tamper or like device.

This application is a division of our copending application Serial No.405,724, led August 6, 1941, and entitled Electromagnetic motor.

Many attempts have been made prior to our invention to construct acompact and eilcient reciprocating electromagnetic motor, but theseattempts have not been entirely successful in that the devices wereheavy, operated at low efciency and were incapable of delivering largeoutputs of power without destructive overheating.

The prior devices also were unsuited for use as soil tampers becausethey could not produce a sufliciently long stroke to effect an adequatetamping of the soil and were, by virtue of their short strokecharacteristic, limited in their application to percussion tools, suchas hammers, chisels, breakers, rock drills and the like.

The present invention is directed to the prevision of an electromagneticmotor of the character above discussed and it is an object of ourinvention to provide a motor which overcomes the above noteddisadvantages and which is relatively compact and eilicient inoperation.

Itis also an object of our invention to provide an electromagnetic motorof the reciprocating type employing a plunger which is reciprocated bythe alternate energization of opposed electromagnets.

It is an additional object of our invention to provide a motor of thecharacter set forth in the preceding paragraphs in which a novel form ofelectromagnet winding is employed to reduce the self-inductance of thecoil to thereby increase the speed of action of the motor and to providefor a higher operating efliciency than has been hitherto possible toreduce the size and weight of the device.

It is a still further object of our invention to provide anelectromagnetic soil tamping device in which the soil engaging tampingfoot is secured to the plunger of a reciprocating electromagnetic motorto be reciprocated therewith.

It is also an object of our invention to provide a soil tamping deviceof the character set forth in the preceding paragraphs in which thestationary opposed electromagnets are mounted for longitudinal movementindependently of each other.

It is additionally an object of our invention to provide a soil tampingdevice of the character set forth hereinbefore which includes a positivestop means for limiting the movement of the electromagnets toward eachother and aj resil- 5 ient stop for yieldably limiting the movement* ofthe magnets away from each other.

Other objects and advantages of our invention will be apparent from astudy of the following specification, read in connection With theaccompanying drawing, 'wherein Fig. 1 is a perspective view illustratingthe electromagnetic motor of our invention as embodied in a soil tampingmechanism;

Fig. 2 is an enlarged elevational view of the l5 mechanism illustratedin Fig. 1 with parts broken away and other parts shown in section toillustrate the details of construction;

Fig. 3 is'an elevational view similar to Fig. 2 but taken in a directionat right angles to the direction of the view in Fig. 2; 4and Fig. 4 is across sectional view taken substantiallyalong the line IV-IV of Figs. 2and 3.

Referring to the drawing, wel have illustrated in Fig. 1 a soil tampingmechanism which is powered vby means of an electromagneticmotorconstructed in accordance with the preferred embodiment of ourinvention. The mechanism illustrated in` Fig. 1 comprises opposed upperand lower electromagnet structures I and 2 which are supported in amanner to be described here-V inafter within a stationary framestructure 3 fitted with handles 4 or'other suitable appurtenances forholding and supporting the device While in operation. The magnets l and2fare adapted to' cause reciprocation of a plunger 5 rto which ispermanently secured a supporting structure 6 carrying at its lower end atamping foot' structure 1.

The tamping 'foot 1 preferably vcomprises a plurality of shortparallelly extending bars 8 interconnected as by means of a cross tiemember 9 to which the connecting device y(i is secured. Each of the barmembers 8 has preferably a trapezoidal cross section, beingcharacterized particularly'by upwardly and outwardly sloping side wallsI0 defining a relatively small at under surface I I. This form oftampingfoot `is preferred to the older forms of tamping feet previouslyemployed and characterized by presenting a large surface area to thesoil to be' tamped because the large area devices served to tamp,compact and harden only the upper layer of soil' being tamped, with theresult that there lwas'pro-- 55 duced merely a hard crust upon thesurface,-

whereas the tamping foot of the character above described penetratesbelow the surface of the soil being tamped and effects a compacting ofthe soil from the bottom up so that when the tamping operation iscompleted, the entire body of soil is suitably compacted.

Each of the stationary electromagnet structures I and 2 is preferablyconstructed as illustrated in detail in Fig. 2 and includes asubstantially cylindrical shell portion I2 of a suitable magneticmaterial internally bored as indicated at I3 to provide a cylindricalrecess within which an electromagnet coil I4 is received. The coil I4 ispreferably wound upon a spool consisting of an inner cylindrical spoolshank I5 formed of a suitable non-magnetic material and carrying spoolend flanges I6 and |`I formed of a suitable insulating material such asfiber, Bakelite, or similar substance.

In winding the magnet I4, there is preferably rst wound an innermostlayer I8 of insulating material such as glass tape, mica-paper orasbestos tape (a preference being expressed for those insulatingmaterials capable of withstanding relatively high temperatures). spoolshank I5 there is then wound a plurality of independent coaxialmulti-layer solenoid coils I9, each of the coils I9 being insulated fromadjacent coils as by means of interposed layers 2U of a heat-resistantinsulating material.

Exteriorly of the spool ends I6 and I'I' we position inner and outerterminal rings 2| and 22 suitably insulated from the coil I4 and fromthe magnet structure I2 as by means of insulating material 23. Liketerminals of each of the coils I9 are connected by conductors to thering 2|, for example, and the opposite like terminals of the coils areconnected by means of conductors to the ring 22. Thus the rings 2| and22 comprise input and output terminals, respectively, for all of theindividual coils I9, which coils are connected in parallel between suchinput and output terminals.

By employing a plurality of solenoid coils I9 mounted coaxially withrespect to each other and connected in parallel in the manner abovedescribed, we have been able to provide a solenoid capable of producinga relatively large magnetomotive force which is characterized by havinga relatively low self-inductance. It is important to keep theself-inductance of the coil as low as possible since the speed of actionof the electromagnetic motor is limited primarily by the selfinductanceof the coil. Furthermore, coils having a high self-inductance causeburning and rapid destruction of the contacts which are employed toenergize and de-energize the coils.

After the coil is assembled, it is rpreferably impregnated with cementor other impregnating material having the property of withstandingrelatively high temperatures and having reasonably high heatconductivity. One such impregnating material which we have found to beeminently satisfactory consists of a mixture of extremely Ane sand andLuminite cement with water, which mixture after impregnation sets toform a hard, solid and mechanically strong onepiece structure. Luminiteis a special Portland type cement manufactured by the Atlas CementCompany and characterized particularly by having an extremely lowshrinkage and rapid setting characteristic.

The coil structure thus formed is retained within the cylindrical recessI3 as by means of a cover Upon the ifi plate 24 which is suitablysecured to the outer ends of the magnet shells I2.

The interior bore of the spool shank I5 serves as a guiding bore forreceiving a cylindrical portion 25 of the plunger 5. The end of thecylindrical portion 25 is preferably provided with a conical or taperedform indicated at 26 to coact With a similarly tapered cone-shapedrecess 2l formed in the innermost end of a xed stop member 28 formed bypreference integrally with the end cap member 24. Upon energization ofthe solenoid coil I4, the plunger is drawn upwardly to bring the conicalend 26 into engage ment with the conical recess 21.

Magnetic sticking of the plunger to the stop member 2B may be avoided bylining the conical recess 21 with a thin layer 29 of non-magneticmaterial such as manganese steel or other suitable alloy having therequisite strength and hardness. Cushioning of the plunger or resistanceto upward movement of the plunger resulting from air being trapped inthe conical recess 2'I may be avoided by providing a breather opening 3]extending into communication with the exterior of V the magnetstructure.

The lower portion of the magnet shell 5 is preferably formed ofconsiderable thickness and provided with a tapered throat portion orentrance aperture 3| which is adapted to coact with a similarly taperedportion 32 of the plunger 5. The plunger 5 is enlarged at its centralportion as indicated at 33 to provide a pair of the tapered conicalportions 32 which extend in opposite directions from the enlargement 33,

The lower end of the plunger 5 is preferably identical in form and shapeto the upper end which is illustrated in Fig. 2 and the lower magnetstructure 2 is preferably identical in construction with the magnetstructure I above de scribed.

At this point attention is particularly directed to the enlarged centralportion 33 of the plunger 5, the coned sections 32 adjacent thereto, andthe similarly coned throat portion 3| which is provided on each of themagnet structures I and 2.

By forming the surfaces 3|-32 and 25-27 as cones rather than as radiallyextending plane surfaces, a much longer stroke is permissible withoutproducing an excessive air gap between the plunger and the componentparte of the magnetic circuit formed by the stop member 2S, the shell |2and the throat portion 3|. This long stroke characteristic is ofparticular utility when the motor is employed as a tamping device.

The magnet structures I and 2 previously referred to are identical inconstruction and supported independently of each other within thesupporting frame 3.

The supporting frame 3 preferably comprises a pair of para-Hellyextending rail members 34 and 35 closely embracing the sides of themagnet structures I and 2 and being interconnected at opposite ends bymeans of cross pieces 36 and 3l. The members 34-31 may conveniently beformed integrally with each other. The magnet structures I and 2 areslidably supported between the rail members 34 and 35 as by securing toeach of the magnet structures a pair of longitudinally extending cleatmembers 33 and 3S deiining guiding,r channels within which the railmembers 34 and 35 are received. Movement of the magnet structures I and2 away from each other is preferably yieldably limited by means ofcompression springs 40 and 4I interposed between the magnet unit Iandcross piece and between the magnet unit 2 and cross piece 31,respectively. Movement of the magnet structures I and 2 towardeach otheris preferably limited by means of positive stop members 42 and 43 whichmay conveniently comprise cleats suitably secured as by welding to theinner surface of each of the rail members 34 and 35 and disposed in aposition to be engaged by the adjacent ends of the magnet structures Iand 2.

The connecting member 6, which serves to interconnect the plunger 5 andthe tamping foot 1, may conveniently comprise a pair of longitudlnallyextending'members 44 and 45 disposed on opposite sides of the lowermagnet structure 2 and having inwardly turned upper ends 46 and 41 whichmay be permanently secured as by welding 48 to the enlarged centralportion 33 of the plunger 5. The lower ends of the members 44 and arepreferably turned inwardly toward each other, as indicated at 49 and 50,to abut the cross tie member 9 to which the ends 49 and 50 are suitablysecured as by Welding.

The magnet structures I and 2 are alternately energized and de-energizedby any suitable switching device connected between a suitable source ofelectrical energy and thel coils I4 to effect a reciprocation of theplun-ger 5. By virtue of the connecting means 6, the tamping foot 1 iscaused to reciprocate with the plunger 5 so It will be noted from theforegoing that the plunger is permitted unlimited upward movement uponenergization of the upper magnet structure I with the result that theupper end of the plunger will engage the upper stop 28. This serves todivide the momentum of the plunger between the plunger and the uppermagnet structure I, causing an upward sliding movement of the magnetstructure I .within the supporting frame 3 and resulting in acompression of the spring 40. Upon de-energization of the upper magnet Iand the energization of the lower magnet 2, the energy stored in thespring 40 will return the upper magnet structure I to a positionengaging the stops 42 and 43 and will thus serve to produce an initialdownward acceleration of the plunger 5, assisting the tractive effortproduced by the energization of the lower magnet 2. Thus, the tampingblow which is struck by the tamping foot is more severe than would benormally expected since the energy for producing that blow is derived inpart from the upper magnet structure I as well as from the lower magnetstructure 2.

Ordinarily the supporting frame 3 is so positioned that the energy ofthe tamping blow is expended before the plunger engages the lower stopmember carried by the lower magnet assembly 2, but this structure isalso slidably supported within the frame 3 by the lower spring 4I topermit the shock of the plunger striking the lower stop member to beabsorbed in case the supporting frame 3 is elevated to a sufficientheight to prevent the tamping foot 1 from engaging the soil. From theforegoing it will be observed that we have provided a novel form ofreciprocating electromagnetic motor which is characterized particularlyby employing a novel magnet construction resulting in a lowself-inductance of the solenoi:l employed and permitting the solenoid tobe operated with higher eiliciency than has been hitherto possible.Furthermore, the use of the cement or similarhardening, impregnatingmaterial hereinbefore described permits the solenoid coils tosuccessfully withstand the shocks and jars resulting from the operationof the device.

Attention is directed to the fact that the novel magnet constructionherein described provides for a relatively long plunger stroke, thusadapting the motor for use with a soll tamping device of the characterherein described wherein the magnet units are each 1separately mountedand provided with resilient stop members permitting at least a portionof the previously wasted up-stroke energy to be added to the energyproduced on the down-stroke to thus produce a stronger and moreeffective tamping blow.

While we have shown and described the preferred embodiment of ourinvention, we do not desire to be limited to any of the details ofconstruction shown or described herein, except as dened in the appendedclaims.

We claim:

1. In a solenoid for use with reciprocating electromagnetic motors, thecombination of: a tubular coil spool shank; a plurality ofconcentrically disposed and radially aligned multi-layer solenoid coilssurrounding said shank; a pair of annular terminal members surroundingsaid shank and positioned at opposite ends of said coils, said memberseach having an outside diameter substantially equal to the outsidediameter of said coils; securing means for attaching said terminalmembers to said coils in electrically insulated relation thereto; meansconnecting the inner end of each of said coils to one of said terminalmembers; and means connecting the outer ends of each of said coils tothe other of said terminal members.

2. In a soil tamping device, the combination of t a reciprocal plunger;a tamping element connected to said plunger for movement therewith; apair of opposed magnet structures for reciprocating said plunger; andmeans mounting said structures in axial alignment with each other andfor independent axial movement.

3. In a soil tamping device, the combination of: a reciprocal plunger; atamping element connected to said plunger for movement therewith; a pairof opposed magnet structures for reciproeating said plunger; meansmounting said structure in axial alignment with each other and forindependent axial movement; and positive stop means for limiting themovement of each of said structures toward the other.

4. In a soil tamping device, the combination of: a reciprocal plunger; atamping element connected to said plunger :for movement therewith; apair of opposed magnet structures for reciprocating said plunger; meansmounting said structure in axial alignment with each other and forindependent axial movement; positive stop means for limiting themovement of each of said structures toward the other; and resilient stopmeans for yieldably limiting the movement of each of said structuresaway from the other.

5. In a soil tamping device, the combination of a reciprocal plunger; atamping element connected to said plunger for movement therewith; a pairof opposed magnet structures for reciprocating said plunger; asupporting frame for said structures including a pair of parallellydisposed rail members extending longitudinally on opposite sides of saidstructures and having corresponding ends interconnected by cross tiemembers; means mounting each of said structures for and a compressionspring interposed between each independent longitudinal sliding movementalong of said structures and the cross tie member adjasaid rail memberscomprising longitudinal cleats cent thereto.

secured to each of said structures on opposite sides TESSIE S. TRAYLOR,

of each of said rail members to dene guides 5 EDNA T. EISENHAND,receiving said rail members; a stop carried by said JOHN B. TRAYLOR,

rail members in a position to be engaged by each Coeecutors of theEstate of John A. Traylor, of said structures upon movement thereoftoward Deceased.

the other structure to a predetermined position; JOHN B. TRAYLOR.

